Carburetor



Nov. 15, 1927. 1,649,531

F. A. HOWARD CARBURETOR Filed July 27, 1918 I Patented Nov. 15, 1927.

UNITED STATES FRANK A. HOWABD, OF CHICAGO, ILLINOIS.

cnmsunn'ron.

. Application filed July 27, 1918. Serial No. 247,016.

My invention relates to improvements in carburetors and will be fully understood from the following specification taken in connection with the accompanying-drawing.

In this drawing, Fig. 1 is a diagrammatlc central longitudinal section of a carburetor constructed in accordance with my invention; and Fig. 2 is a section on the line 2 of Fi 1, and Sl l OWlIlg a top plan view of the t rottle-valve.

The carburetor of the present invention is particularly intended for use on internal combustion engines operating under a wide range of speed and load conditions, as, for example, on automobile engines. Among the advantages attainable by the carburetor of the present invention the following may be mentioned:

1. The mixture ofvolatile fuel and air is initially formed after the expansion of the air beyond the throttle-valve, so that a fuel of lower vapor tension may be employed;

2. The constant level reservoir from which the fuel is withdrawn into the carburetor is exposed to the pressure within the carburetor, or to a pressure which is a function of this pressure, so that an additional element of control for securing proportionality is added.

3. The changing vapor pressure of the fuel under different temperatures acts as a thermal correction for the proportions of the mixture.

4. The carburetor is capable of lifting its fuel supply from a tank located at a lower level.

5. The minimum depression within the .carburetor is controlled by a throttle-valve of special construction, which operatcspositively under all ordinary running conditions.

6. The fuel admixed with a small propor tion of air is heated in an annular chamber surrounding the Venturi tube before admixture with the main stream of air.

7 An electrical heater is mounted within the heating chamber in such position as to supply its heat mainly to the fuel itself for starting purposes.

Many of the foregoing advantages have been attained to a greater or less extent by carburetor constructions heretofore known, but so far as I am awareno successful carburetor has yet been devised in which there was embodied any substantial proportion-of these principles and advantages. 7

Referring to the drawings- The numeral 10 designates the main air passage of the carburetor, this passage being provided with a manually-controlled throttle-valve 11 at its inlet end, and having a Venturi tube 12 in its outlet section, i. e.,

that section which is designed for attach ment to the intake pipe or manifold of the engine. An annular heating jacket 13 surrounds the outlet end of the carburetor, this jacket being supplied with a heating fluid, such as exhaust gas from the .engine. The cylindrical wall of the air passage 10 is continuous from end to end, so that. there is formed between the wall of the Venturi tube 12 and the annular jacket 13 an intermediate annular chamber 14, which serves as a heating chamber. A sleeve 15concentric with the Venturi tube and spaced from the latter as Well as from the inner jacket wall serves as a deflector for the fuel and air stream initially formed, and as a support for an electrical heating element in the form of a wire coil 16. Slightly beyond the throat of the Venturi tube 12 the latter is provided with apertures 17, which provide for communication between the interior of the tube and the annular chamber between the tube and the sleeve 15. An aperture 12 in the base of the Venturi drains the chamber 1 1.

It will be understood that the showing in Fig. 1 is diagrammatic only and that the parts may be assembled in any desired man-.

ner, the particular design of the individual parts so as to permit them readily to assemble and disassemble for inspection and repair not being a part of the present inven-' tion. 1

' The throttle-valve 11 consists of two relatively movable sections. designated 11, is pinned or otherwise rigidly secured to the shaft of the throttle-valve, and may have the T-form clearly shown by Fig. 2, the stem of the T serving as a means by which this section of the throttle-valve is affixed to the shaft. The second section of the throttle-valve, designated 11*, isfreely mounted for rotation upon the shaft, its movement in one direction, however, being limited by the wall of the air passage, and in the other direction by the section 11, which may have an overhanging tongue 11 which serves this purpose. The two sections of the throttle-valve are connected by a diametri cal tension spring 11, which may be made in two sections, as shown, joined by a straight e5 The first section,

lltll wire so that the body of the spring may lie as close as possible to the face of the throttlevalve. The air passage 10 beyond the throttle-valve 11 is connected with the annular chamber 14, and through the latter with the venturi 12 by a passage 18 having controlling orifices 19 and 20 at its inlet and outlet ends, respectively. Just beyond the control orifice 19, and in aspirating' relationship to the air-jet which issues therefrom, is a main fuel nozzle 21, which may be of the usual form, that is with the nozzle-controlling orifice in the delivery end of the nozzle. This nozzle extends below the normal fuel level in a constant level reservoir 22. The means for maintaining the normal fuel level within this constant level reservoir is diagrammatically illustrated as consisting of a oat 23, having affixed thereto a tapered valve 24, which opens and closes the aperture in the fuel delivery pipe 25. In order to illustrate the possibilities of the carburetor, this pipe is shown as connected with a ill fuel reservoir 26, located below the carburetor and having the fuel therein exposed to atmospheric pressure, as by a vent 27 in the filler cap. The fuel level within the chamber 22 may be regulated by a loading spring 28,

which bears upon the top of the float 23 and is adjustable as to tension by a threaded stem 29 extending through the top of the reser- Voir, and there provided with an adjusting head which is frictionally locked in any adjusted position by a spring 30. The space above the liquid fuel in the chamber 22 is connected with the passage 18 above the fuel nozzle 21 by a tube 31, having one end projecting into the passage 18, this end being preferably turned at an angle, as shown at 32. The tube 31 is preferably adjustable about its axis, so as to vary the inclination of the tube-end 32 to the axis of the passage 18. The top of the float chamber 22 may have a very small atmospheric opening 33.

Beyond the point at which the float chamber control tube 31 enters the passage 18 there is connected the passage 34, which has its other end open to the atmosphere, the opening being formed in a cap 35 provided with an outwardly-projecting nipple 36. An auxiliary jet nozzle 37 opens into the passage 34 near its inlet end, and in aspirating relationship to the air-jet entering through the nipple of the cap 35. The auxiliary fuel nozzle 37 extends level in the chamber 22, and has its controlling orifice 38 formed in its inlet end as by drawing down the latter, as illustrated in Fig. 1.

The carburetor described in the foregoing operates as follows: The heating coil 16 may be connected with a source of current of proper potential, and therebyv brought to a high temperature, the mounting ofthe coil sure within the below the normal liquid being such that heat is not transmitted from it readily to the body of the carburetor. This is of importance, since it would in most cases be impractical to provide a heavy enough current flow to heat the body of the carburetor to a substantially increased temperature. If the engine now be cranked, the throttle-valve 11 being at that time closed or partially closed, there will be created within the float chamber 22 by the connection 31 a pressure substantially below atmospheric, and, because the float chamber is below atmospheric pressure while the reservoir 26 is at atmospheric pressure, the fuel will be withdrawn from the reservoir 26 and discharged into the float chamber 22 to till the latter up to the normal level. Under some conditions, it will'be found convenient for the starting of the motor to prime the carburetor, and this may be conveniently done by screwing down the stem 29 until the pressure of the spring 28 exceeds the buoyant eifort of the float. Under such condi tions fuel will continue to flow into the float chamber until the latter is filled up to the'level of the tube 31. In the meanwhile fuel will have been discharged by gravity through the nozzles 21 and 37, and will finally discharge in a relatively large stream through the tube 31. The priming action thus obtained, particularly by reason of the heavy flow of fuel through the relatively large tube 31, will be sufficient to start the motor under the most adverse temperature conditions. It should be here noted as characteristic of the present type of carburetor that the throttling of the air intake passage to create a substantial sub-atmospheric prescarburetor will materially assist in starting the motor. In addition to the factors named, the startlng of the motor is further facilitated by the direct impingement of the mixture of air and fuel issumg from the orifice 20 upon the heatlng coil 16. The latent heat of vaporization is thus supplied to the fuel, and if condltions are such that it is possible for a combustible mixture to exist, it will be formed and will issue from the orifices 17, into the Venturi tube 12, to pass thence to the engine. en the motor is in operation the stem 29 if same has been lowered will be adj ustcd to permit the float 23 to operate, and to maintain the predetermined constant level within thefloat chamber-Q So long as the throttle valve 11 is kept closed, or nearly closed, the velocity through the main air passage 10 is negligible and the pressure dif' ference between the inlet end of the passage 18 and the throat of the venturi is likewise negligible. Under these conditions the main nozzle 21 will not operate, for the reason that there is no substantial difference in ressurc between this nozzle and the space a ve the liquid level in the float chamber. The auxiliary nozzle 37 will, however, be exposed to the direct aspirating action of the high velocity stream of air entering through the nipple 36, and expanding over the end, of the nozzle. The requisite fuel for idle running is thereby supplied to the atmospheric air entering the passage 34, and the mixture thus formed is delivered to the passage 18, thence to the annular chamber 14 to be heated by contact with the wall of the latter, and finally into the Venturi tube. c

As the motor is put under load, and the throttle-valve opened, the air in the main passage 10 assumes an ap reciable velocity, with a resultant apprecia le pressure drop between the throat of the Venturi and the inlet end of the passage 18, whereby there becomes effective upon the nozzle 21 an aspirating depression suflicient to cause the latter to deliver fuel to supplement that delivered by the auxiliary or idling nozzle 37. Further opening of the throttle with resultant increase in the speed of the motor under the same load proportionately increases the delivery of the nozzle 21;

It will be noted that since the passage 34 which is open to the atmosphere at its inlet end enters the passage'18 beyond the nozzle 21, but on the anterior side of the control orifice 20, the velocity of the aspirating air current through the orifice 19 and over the nozzle21 will be dependent in part upon the absolute pressure within the throat of the venturi instead of being dependent solely upon the difference in pressure between the inlet and throat. The air passage 34 opening at its inlet end to the atmosphere, therefore not only provides the idling mixture through the idling nozzle 37, but cooperates with the delivery from the main nozzle 21 in an inverse manner, i. e., the delive from the main nozzle tends to decrease re atively to the total mixture passing through the outlet 12 as the inward air flow through the passage 34 increases. It will be understood that the air flow through the passage 34 is increased when the valve 11 1s operated 'to restrict air fiow through the passage 18. Since the latter air flow is a function of the absolute pressure or vacuum within the carburetor," and owing to the arrangement of the fuel nozzles a correction factor working in the desired direction for producing a mixture of constant proportions, or even one which is somewhat leaner when a high vacuum exists in the carburetor, is obtained. Thus it will be understood that a high vacuum within the carburetor necessarily indicates a light motor load, and under such load it is necessarily true that economy of fuel rather than maximum power. is the result to be aimed at. p I

The inlet ends of the auxiliary nozzle 37' and auxiliary air passage 3d have been de signed with a view to securing a somewhat smaller variation in the delivery of the respective fluids than is attainable by the use of ordinary constructions. The outwardlyprojecting nipple 36 on the cap 35 at the end of the air passage acts to impose a loss of head and conse uent reduction of delivery of both air and el through the passage 34 and thisrelative reduction oi delivery increases very rapidly as the velocity of the entering air increases. This is due to the fact that the vacuum produced while the valve 11 is closed is eifective to produce a strong flow through the orifice 36, while almost no flow occurs through 19 because what little air does pass the valve 11 follows the passage '10. As the valve 11 opens, moreand more air is drawn through the by-pass 18 with a consequent increase of the amount passing the orifice 19 with no such increase at 36. The delivery of fuel from the nozzle 37 is by the provision of the orifice 38 in the inlet end of the nozzle automatically controlled in a similar manner.

With the throttle 11 nearly closed as in the idling position, very little air passes through the venturi so that there is no tendency to aspirate air through the bypass 18. What air doesass the throttle valve 11 will pass throug the straight tube 10 and almost none of it will be drawn through the openings 17 and through the restriction 19 from the lower end of the by-pass 18. This is particularly true since air passin through the opening 36 will, at idlin spee practicallysupply the demands of t e vacuum produced by suction of the venturi through the openings 17. At this speed a large part of the total supply of air will passthrough the opening 36.

Under load conditions however With the valve 11 open or partly open, uite the reverse is true. A heavy charge 0 air passing the venturi will produce a heavy vacuum in front of the openings 17 thereb drawin a heavy charge of air through the y-pass 1% so that a relatively large proportion ofthe ingoing air will be drawn through the bypass 18 while at the same time, owing to the fact that the opening 36 is preferably made smaller than the constriction'19, only a relatively small amount of air will pass through the opening 36.

It has hi herto been an objection to all forms of carburetors or motor'a'ccessories, where the vacuum of the intake manifold is transferred to the surface of a body of the fuel, such as the so-called vacuum fuel feed tanks, that they would under some conditions seriously disturb the proportions o the mixture by reason of the delivery of fuel vapors into the carburetor, or directly into the intake manifold, as the case might be. For example, an ordinary grade of gas 'olene used for fuel in motor vehicles has llhtl a vapor tension of approximately 300 millimeters at F., this vapor tension increasing .very rapidly and becoming practically one atmosphere at 100 F. It is no uncommon thing for the body of a carburetor, or a vacuum fuel feed tank to attain temperatures between 70 and 100 F., or even in excess of this latter figure, and since the depression or vacuum within the carburetor, where the latter is provided with an anterior throttle, or in the intake manifold, exceeds one-half atmosphere Where the motor is turning rapidly under a light load and a closed throttle, it will be seen that the fuel may actually boil-or fractionate off a considerable proportion of its lighter constituents, and these vapors entering the carburetor or the manifold seriously disturb the proportions of the mixture, particularly since the very condition of maximum vacuum or depression within the manifold which causes this vaporization of the fuel is that condition in which the smallest amount of air is being admitted.

In the carburetor of the present invention this condition of high vapor tension of the liquid fuel, which has hitherto operated to disturb the proportions of the mixture wherever a liquid body of the fuel was exposed to the depression within the manifold, is made to operate as an automatic thermal correction. Thus, it will be seen that whenever the temperature of the fuel within the constant level reservoir 22 is such that its vapor tension is equal to or exceeds the depression within the central portion of the passage 18, fuel vapors will be delivered through the tube 31 to this passage, and as a result of such delivery of vapors the velocity through the orifice l9 and consequently the delivery of liquid fuel from the nozzle 21 will be reduced. Not only does the phe-' nomenon described therefor fail to disturb the proportionality of the mixture, but it may even be advantageously employed as a correction factor offsetting the decrease in viscosity of the liquid, which tends to increase the delivery of the liquid nozzles, This correcting action may be obtained'at all temperatures, and with fuels of all measurable vapor tensions by the provision of the atmospheric bleeder opening 33 into the float chamber 22. By providing such an opening there is established a constant flow of air above the liquid level in the float chamber, the tube 31 therefore supplementing the tube 34 as a bleeder device for the passage 18. The quantity of vapor delivered by the tube 31 will be seen to depend upon the vapor tension of the fuel in the reservoir, and the vapors of this fuel will be delivered to the passage 15 to exercise according to their amount the desired temperature controlling function whether the depression within the constant level reserthe voir is greater than or less than the tension of the fuel.

It has been found that if the Venturi tube 12 is of adequate size to deliver the quantity of mixture required under the maximum load and speed of the engine, it will quite generally need to be so large that the depres sion at the throat thereof with wide open throttle and minimum motor speed may be insuflicient to lift the liquid fuel from the low level tank to the constant level reservoir. To correct this condition, and, fur thermore, to limit the minimum vacuum under which the carburetor operates so as to avoid those erratic fuel delivery phenomena which are met withat exceedingly low heads, I provide the special form of throttle valve 11 described. Under all ordinary conditions of operation this throttle valve will respond solely to the manual control, the section 11 being positively controlled as described, and the section 11 being constantly held in convapor tact with the stop of the section 11 by the impact of the air upon its lower face. In the event of the throttle being fully opened, however, while the motor is operating at its lowest speed, the tension of the spring 11 will be sufficient to hold the throttle section 11 in contact with the wall of the air passage, and thus partly obstruct the latter, maintaining a minimum difference in pressure between the two sides of the throttle. As the motor speed increases this springheld section of the throttle will automatically open without imposing any further resistance to the flow of the air, the angularity of action of the spring being such that the automatically moving section of the throttle-valve imposes a resistance of the same character as would a gravity loaded valve.

While I have described in considerable detail a specific embodiment of my invention, together with my theories as to the manner in which the same functions, it is to be understood that this is illustrative only, and for the purpose of making clear the naice ture and mode of application of the invention,"and that I do not regard the invention as limited to the construction described, nor dependent upon the soundness or accuracy of the theories which I have advanced, except in so far as they may be included within the terms of the accompanying claims in which it is my intention to claim all novelty inherent in the invention as broadly as is permissible, in view of the prior art.

What I claim is:

1. In a carburetor, an air passage, a Venturi tube forming a part of the air passage, an annular jacket surrounding the tube and having an inner Wall forming with the wall of the venturi an intermediate annular chamber, means for supplying heating fluid to said jacket, and means for delivering a mixture of fuel and air to the intermediate annular chamber to be heatedtherein, said'annular chamber communicating with the venturi.

2. In a carburetor, an air passage, a Venturi tube forming a part of the air passage, an annular 'jacket surrounding the tube and having an inner wall forming with the wall of the tube an intermediate annular cham her, an electrical heating element mounted within the said chamber, means for supplying heating fluid to the said-jacket, means for delivering'amixture of fuel and air to the intermediate annular chamber to be heated therein, and openings communicating said chamber and venturi.

3; In a carburetor, a. main air passage having a constriction therein, a by-pass del vering into said constriction, an opening in said by-pass communicating with the atmosphere, a fuel delivery nozzle opening into said by-pass, and a throttle anterior to said constriction and by-pass.

4,111 acarburetor provided with an an- "terior throttle, a main air passage having a venturi therein, a by-pass delivering into 1 said venturi near its narrowest part, a main fuel nozzle opening into said by-pass, a constantly open atmospheric inlet opening into said by-pass, and an auxiliary nozzle in operative relationship to the said atmospheric inlet.

5. In a carburetor provided with an anterior throttle, a main air passage having a constriction therein, a bypass around the constriction and communicating therewith, means for delivering fuel into the said bypass, an atmospheric opening in the said by-pass, and additional fuel delivery means operable by the atmospheric air entering the by-pass through said atmospheric opening.

6. In a carburetor provided with an anterior throttle, a main air passage having a constriction therein, a by-pass around the said constriction and communicating therewith, a constriction in the said by-pass, a constant level fuel reservoir, a nozzle opening -into the said reservoir and delivering into the by-pass in aspirating relationship to the constriction therein, means for admitting atmospheric air to the said by-pass beyond the constriction, an auxiliary fuel nozzle in asparating relationship to the atmospheric air stream entering the by-pass through said means, and means for applying to the surface of the fuel in the said reservoir the depression existing in the b -pass beyond the second mentioned constriction.

FRANK A. HOWARD. 

